The present invention relates to a sheet-like light source device. More particularly, it relates to a sheet-like light source device which is employed as a backlight of a liquid crystal display device, wherein the sheet-like light source device is capable of preventing degradations in display qualities owing to anomalous emission without degrading the brightness thereof.
A sheet-like light source device as illustrated in FIGS. 5 and 6 is conventionally used a backlight in a liquid crystal display device. Such a conventional sheet-like light source device is composed of a lamp 21 serving as a rod-like light source, a lamp reflector 22 serving as a tubular reflecting member, a light-conducting plate 23, and a reflecting sheet 24 serving as a planar reflecting member. The lamp 21 is mainly comprises a cold-cathode fluoresent lamp (CCFL), and light emitted from the lamp 21 is made incident on the light-conducting plate 23, either directly or via the lamp reflector 22. A transparent material is used as the light-conducting plate 23, and polymethyl methacrylate (PMMA), polycarbonate (PC) or glass exhibiting high transmission rate of light is generally used.
As illustrated in FIG. 6, light which is made incident on a light-incident surface 23a of the light-conducting plate 23 is spread through the light-conducting plate 23 to a side opposite of the lamp while repeating total reflection through a difference in refractive indices of acrylic resin and air. All of light made incident from the light-incident surface 23a of the light-conducting plate 23 will satisfy a total reflection condition and will not be emitted from a front surface 23b or a rear surface 23c of the light-conducting plate 23. The rear surface 23c of the light-conducting plate 23 is thus devised to emit light therefrom to the front surface 23b, which is generally achieved by forming a scattering portion (not shown) mainly through white printing. Light will be scattered when hitting against this scattering portion to thereby break the total reflection condition of light within the light-conducting plate 23 so that light will be emitted from the front surface 23b which is a display surface side of the light-conducting plate 23. This scattering portion is made of a material which does not perform absorption, but performs only scattering of light. Light which that has been scattered at the scattering portion will be also scattered to the rear surface 23c which is a non-display surface side of the light-conducting plate 23 so that the reflecting sheet 24 is placed on the rear surface 23c for reflecting this light to the front surface 23b on the display surface side. The reflecting sheet 24 is generally disposed to extend to the interior of the lamp reflector 22 as illustrated in FIG. 6.
While light which is made incident on the light-incident surface 23a, which is a surface end portion on the lamp 21 side of the light-conducting plate 23, shall ideally be spread by entering the light-conducting surface 23 and through total reflection in the above-described manner, light might slightly penetrate from portions A of the front surface 23b and the rear surface 23c proximate to the light-incident surface 23a exposed to the interior of the lamp reflector 22 in actual conditions. Light which is made incident from the portions A of the front surface 23b and the rear surface 23c will not satisfy the total reflection condition within the light-conducting plate 23 but will remarkably degrade display qualities owing to generation of anomalous emission (emission line) on the display surface proximate to the lamp 21.
For reducing anomalous emission (emission line) in the proximity of the lamp 21, it has been conventionally disclosed for a technique as one example for reducing light made incident from the rear surface 23c, for instance, in Japanese Unexamined Patent Publication No. 304627/1997, in which a reflecting sheet 24 is made to project from the light-conducting plate 23 within the lamp reflector 22 as illustrated in FIG. 7. However, the rate of light which has entered in a space 22a on a rear surface side of the reflecting sheet 24 projecting within the lamp reflector 22 and which will again be reflected is small, and thus light which has entered in the space 22a will mostly be useless.
Japanese Unexamined Patent Publication No. 112214/1998 further discloses a technique for reducing the amount of light made incident from the portions A of the front surface 23b and the rear surface 23c wherein the lamp reflector 22 is made to jut out by a minute distance in a direction parallel to the display surface of the light-conducting plate 23. However, the light-incident surface 23a might be exposed when relative positions of the light-conducting plate 23 and the lamp reflector 22 are shifted from designed values owing to assembling errors or application of force, which also leads to remarkable degradations in display qualities.
The present invention has been made for the purpose of solving these problems, and it provides a sheet-like light source device capable of preventing degradations in display qualities owing to anomalous emission without degrading the brightness thereof.
In accordance with the present invention, there is provided a sheet-like light source device of side-light type comprising a light-conducting plate made of a light-transmitting material, at least one rod-like light source disposed proximate to a light-incident surface comprising at least one lateral side end portion of the light-conducting plate, a tubular reflecting member covering portions other than a surface facing the light-conducting plate of the rod-like light source, and a planar reflecting member disposed proximate to a position facing a rear surface of the light-conducting plate,
wherein an end portion of the planar reflecting member is projecting out from an end portion of the light-conducting plate within the tubular reflecting member, and
wherein the projecting end portion of the planar reflecting member is bent in a parting direction from the rod-like light source.
It is preferable that the projecting end portion of the planar reflecting member is bent within an interior of the tubular reflecting member.
It is preferable that the projecting end portion of the planar reflecting member is bent upwardly back and that an edge of the projecting end portion is abutting against the light-incident surface of the light-conducting plate.
It is further preferable that a throttle is formed on an aperture into which the light-conducting plate of the tubular reflecting member is inserted, that the projecting end portion of the planar reflecting member is bent downwardly back, and that the edge of the projecting end portion is abutting against an inner surface of the throttle of the tubular reflecting member.
It is preferable that the bent back portion on the projecting end portion of the planar reflecting member is adhered to an opposing portion of the planar reflecting member.
In accordance with the present invention, there is further provided a sheet-like light source device of side-light type comprising a light-conducting plate made of a light-transmitting material, at least one rod-like light source disposed proximate to a light-incident surface comprising at least one lateral side end portion of the light-conducting plate, a tubular reflecting member covering portions other than a surface facing the light-conducting plate of the rod-like light source, and a planar reflecting member disposed proximate to a position facing a rear surface of the light-conducting plate,
wherein the tubular reflecting member is jutting out by a specified distance in parallel to the light-conducting plate to the rod-like light source side, and
wherein a distance between a bend end portion of the tubular reflecting member and a rear surface of the tubular reflecting member on the rod-like light source side is set to be at most equal to an outer diameter of a shock absorbing member disposed around the rod-like light source.